Fuse rating for electric car heating system?

[dalathegreat]

Hi experts!
I'm doing a fuse replacement in a power distribution module on a Nissan Leaf. This is what it looks like.

It's a glass fuse, 32mm long. Rated for slow 30A 500VDC.

I had my electrician father pick up a 30A fuse, but he accidentally picked one that was rated for 250VAC max. So I'm hunting for fuses. I ordered a fuse from the other side of the world, but it got me thinking how hard it is to source a high voltage DC fuse. I have some questions

• Is it OK to use a fuse rated for 500VAC on a system that will see a bit under 400V DC max?
• Some sources say that you should use ½ the AC rating on DC systems, any truth to this?
  
• Why do manufacturers not state a DC voltage rating?

I found ONE fuse that is stocked in my town, but it's 500VAC https://www.starelec.fi/product_info.php?cPath=66_461_487&products_id=26301 Maybe won't be enough?

Cheers for any expertise!

 

[davenn]

Is it OK to use a fuse rated for 500VAC on a system that will see a bit under 400V DC max?

it's a car/vehicle where is the 400V coming from ?

 

[dalathegreat]

it's a car/vehicle where is the 400V coming from ?

Yes, the main battery when fully charged on the vehicle outputs 396V

 

[Hunter64]

That's the problem with vintage cars, spare parts are hard to get

 

[davenn]

Yes, the main battery when fully charged on the vehicle outputs 396V

ohhh ... this is an electric vehicle ? didn't realise that from your first post

 

[bertus]

Hello,

Looking at the picture, it looks like the fuse has tabs on both sides.
They look more like the fuses on this page of the site you gave:
https://www.starelec.fi/index.php?cPath=66_2536

Keep track of the size of the fuse when you order one.

(I can not read what is given as it is in finnish).

Bertus

 

[Tha fios agaibh]

Pull the old fuse and look at the markings on the metal end of the fuse.

I wouldn't use a 500v ac rated fuse for 400v dc. There's a chance it could arc over and not safety clear a fault.

I have heard the "1/2 the ac rating" rule of thumb and although its not an accurate calculation, it seems a safe approximation.

Manufactures don't state DC ratings on some fuses because they are not designed to interupt DC current.

At that voltage, its best to wait for a properly rated fuse.

 

[dalathegreat]

Thanks for the input, I will wait for the proper 500VDC fuse to arrive in the mail!

 

[Bluejets]

I'm curious why the fuse blew in the first place.
Doubt there would be any 500v dc or anywhere near it being interrupted in any case.

 

[dalathegreat]

I'm curious why the fuse blew in the first place.
Doubt there would be any 500v dc or anywhere near it being interrupted in any case.

The PTC heater shorted out and blew the fuse. More info here https://www.mynissanleaf.com/viewtopic.php?f=30&t=30738

 

[bertus]

Hello,

Here I got some pages with fuses that look like yours.
It is an copy of the pages 48 and 49 from the following book in the link:
http://www.jabse.com/dl2.php?file=L...ldHMvRnVzZSBCaWJsZSBDb21wbGV0ZSBHdWlkZS5wZGY=

Bertus

 

[dalathegreat]

Thanks, I ultimately went with the recommendation of other Leaf fixers, and ordered this fuse https://fi.farnell.com/mersen-ferraz-shawmut/16543/fuse-hrc-am-32a/dp/1436845?st=400VDC 32A